Electromechanical telephone switching system



- ILI Q'IROIBCHANICAL TELEPHONE SWITCHING SYSTBI Filed lay 23. 1924 Jwadian- TON 5/ Ll 10a zoo r Patented Mar. 12, 1929.

- UNITED STATES PATENT OFFICE.

' -FRI'1Z ALDENDORFF, OF BERLIN-WILMERSDORF, GERMANY; CHARLOTTE ALDEN. DORFF I'IEIEESS OF SAID FRITZ ALDENDORFF, DECEASED.

E EcTnoMncHAnIcAL urnnnrnonn'swrrcnrne SYSTEM.

Application filed May-23,1924, serum No. 715,433, and. in Great Britain June-11, 1923.

This invention relates to electromechanical telephone switching systems and its object is to provide an efficient and yet simple linefinder or revertively acting trunk-finder starting-arrangementby which a calling party is enabled to send in his impulses upon the response of his line relay and, as a rule,

without waiting until a finder brush has travelled up to a bank contact connected'to or associated with his line. This object is accomplishe'd by providing for a group of subscribers or trunk lines, which are multipl'ed to the bank contacts of a set of finders, a transitorily engaged dialling trunk adapted to be automatically connected after each use by a trunk finder to a tree trunk and to be connected to a calling line by a relay associated therewith the moment the line is placed in a calling condition. A trunk finder is pro vided whose hunting action isstarted by an impulse sent from a line finder whose hunt ing operation is initiated by the and ot a circuit that extends through a calling trunk or subscribers line. "The stopping or test relay circuit of the line finder is directly controlled by a contact of the release relay of the numerical switch associated with the line finder. To relieve the relay individual to each subscribers line or calling trunk line of the 0 necessity of moving alarge number of contacts when only energized by a current that has to fiow over a subscrlbers line, a common relay may be provided by which a local circuit through a winding of the subscribers line relay is closed so as tdcause this relay to move a heavily loaded armature that moves a considerable number of contacts.

The invention is shown in the drawing in which H Fig. 1 shows an arrangement in which each line is'provided with a relay equipped. with a slowly retracting armature. r

' In Fig. 2 a modified arrangement is shown in which there is only one slow-acting relay for a whole group of subscribers.

In Fig. 1 a subscribei"s station 1 isshown connected by a line 2, 3 to a set of bank contacts in a group of finders of which one line finder LF is shown. The subscribers line is also connected through the contacts of a cutoff relay 5 to a line relay 41 wliich,lwhe n it'attracts'its armature (diagrammatically illus trated in the drawing) connects thesubscribers station to a dialling trunk 7 connected to a trunk finder TF. The'trunk finder is arranged to preselect a tree trunk such as 20 21', that forms a connecting link between a line finder ill? and a numerical switch NS or the like, which may be a'group selector or aconnector. I i

As this invention only relatesto'. the line finder part of the exchange the following detailed description of the circuits will be limited chiefly thereto. When the subscriber 1 calls by raising his receiverya current flows from the positive pole of the battery through contact 25 of a relay 6 common'to a group of subscribefis wires 26, which is multipled to' the-contacts of allthe relays like 44 and 5 associated with the various lines, contact 27 ot' the cutoff relay 5, wire 2, subscribers station 1, wire 3, contact 28 line relay 1, contact 29, contact 30 of common relay 6 to the negative pole. The line relay 1 is energized and opens its contact 31 so as to render the calling line engaged at the contact banksof the connectors (notshown). The line relay 4; also opens its contact 29, after previously closing its contact 82 so as to maintain itself energized. It also'closes its contacts 38, 341 and 35. f By contact 33 it connects the cut-off relay 5 to the bank contacts lilte'36, in the banks of the finders, like LF. By the contact 34 a circuit is closed through the common relay 6 which opens'its contacts 30 and 25 and thus for a brief interval prevents any other, line relay like 4; in the same group of subscribers romfbeing energized by another call ing linein the same group being placed in the calling condition. The positive pole of the battery, which is disconnected at the con tact 25 from thewire 26 is .recon'nected to this wire by the contact 35 through the transitorily engaged dialling trunk 7, which will be connected at this moment, as hereinafter describedg'to the impulse relay 19 of affree trunk 20, 21. Ilencecurrent will novv'flow I through the line relay 4 of'the calling subscriber'over the follbwingpath: from the positive pole-through thewinding of the im-' pulse relay 19, wire 36, wiper 8, contact j of the re-lay12, dialling trunk 7, contact 35. contact 27 wire 2, station 1, wire 3; contact 28, line relay l contact 32 to the negative pole. The subscriber may therefore commence sending 'in' numerical impulses im[ mediately after raising his receiver without. Waiting for his line to be connected through to a tree trunk by the hunting wipers oi any kind of selector switch, When the impulse relay 19 is energized, a circuit is closed through the release relay 38, this circuit eX- tending; from the minus pole through cont-act 10, release relay 38, resistance 1-1 to the positive pole. The release relay closes its con tacts 42, 1-8 and opens its contact 44. By contact 43 an energizing circuit for the driving magnet 17 of the line liuder LF is closed which extends from the negative pole through 13, contact 15 of the test relay 17, driving magnet 1'4", impulse producer IP to the positive pole. The impulse producer 11 has a Winding; of a very high resistance and attracts its armature 18 which short circuits the high rec net 1? strong. enough to energize it. The impulse producer then allows its armature to drop bacl due to the short circuit through the contact 153, and the high resistance thus reinserted in the circuito'l' the magnet 17 causes the armatiu'e ot the latter to drop back.

The impulse producer then'again attracts its armature and short circuits its high resistance to reenergizc the magnet 17. This sequence of events is repeated until the wiper 15 of the line finder ill? strikes the bank contact '36, when the test relay or stopping relay is energized by a current which flows from the negative pole through 13,417, 15, 36, 33, cutoit relay 5 to the positive pole. The stopping relay 4-7 closes its contacts 18, 19, and 46 and opens the c1r cuitot the driving magnet 1'? at contact .now proceed through the wipers 13, 14; of the line tinder LF through the following circuit: positive pole oi. the hattery, left hand winding 01'' 19, trunk wire 20, 18, 13, hank contact 51, 2,-statioi1 1, 8, banl: contact 52, 14-, {19, 21, right hand. winding of the impulse relay 19 to the negative pole. /Yhen the armatlu'es ot the impulse relay 19 oscillate in responseto the dialling impulses, a series oi switch impulses is. sent, first through the group selecting magnet 22 or tens magnet and then, after the change-over, to the individual line selccting uagnet or units magnet 2,3 of the numerical switch NS, which may be a switch ofthe kind described with reference to Fig.2 01' my British ,Patcnt The moment the 'wipers 13, 14, 15, 16 ot the line finder are set onto the calling line,

and the stopping-relay 47 is energized, the

f'trunlrfinder TF is started to hunt for another tree'trunk: This starting operation is 12 is deenergizcd.

ance winding so as to enable a current to iiow through the drlvingmag net 11 of a trunk finder and this magnet then continues receiving impulses until the relay The energization of the relay 12 continues as long as the wiper 10 strikes hank contacts connected to wires like that lead to engaged trunks; tor the release relays 38 of engaged trunks will all be energized and will thus connect the positive pole through a contact like 61 tothe'ir wires 60' and the ri 'ht hand windin of the relav 2 ro h .1

12 will thus lie kept energized by currents 'flowin itrom the iositive )ole to contacts like 61 and wires like 60, wiper 10 andconta'ct 57. During the travel of the wiper 10 11pm one bank contact to another the relay '12 is maintained energized by the left hand windingreceiving impulses from the positive pole, impulse producer, Contact 58 and the wire 65. The moment the wiper 10 reaches a wire like 60 leading to disengaged trunk, the

"right hand winding of the relay 12 is deprived oicurrent, and as the 1e t hand winding 01'? the role will also he curreutless at this moment the relay12will allow its armature to drop back so that the circuit of the magnet 11 is-opened at'58 and the dialline trunk 7 is connected through the contactSi and the wiper 8 to a Wire like 36 leading to the impulse relay like 19 ot a disengaged trunk like 20, 21. The diallingtrunk will then be ready to conduct dialling impulses from another calling line to another tree trunk In Fig. 2 the relays associated with the calling lines are modified. hut all the other parts of the dialling trunk ant finder start ing arrangement are precisely similar to the arrangements in Fig. 1. The line relays 104, in Fig; 2 are providedwith two armatures, an easily moved armature which operates the contacts 134, 136, and a heavier armature,

whichoperatesthe contacts 131,133, 135, 13 7, 138. The common relay 106, which allows ,its armaturcs 125, 126' to'retract slowly, is

first energized in parallel with the line windmg 104 of ahne relay, andthen the left hand \vindin 10slot the line role 1 is energized CD i.

the. positive pole through 125, wire 126, contact 137, inding 1041-, contact 128, Wire 103, station 101,'wire 102, contact 127, contact 138 to the negative pole. The line relay,'hy its easily moved armatures, closes its contacts 134, 136 and the common relay 106 is then energized in parallel with a winding 10 1. The relay 106 then closes a local circuit to the winding 104 which extends from the positive pole through 126, 136, 10 1, to the negative pole. The heavier armature of the line relay is then attracted so that the contacts 133, 131, 137, 135, 138 of the line relay are operated. By the opening or the contact 125 of the common relay 106 the energization of other line relays is prevented until the dial ling trunk 7 is released for another call as explained in connection with Fig. 1.

The line relays in Fig. 1 are provided with a coil 200 connected to a tone producer (not shown) which gives rise to a tone in the re' ceiver oi a calling station in case the line relay 4 is not immediately energized when the call is made. In Fig. 2 asimilar tone producer coil 200 is provided in connection with the common relay 106. In this Case the tone is only heard at the calling station when the line relay or the same is energized.

I claim V 1. In a telephone exchange system, a plurality ot line finders having bank contacts and cooperating wipers, a group 01 lines multipled to said bank contacts, link circuits terminating in said wipers, a. numerical switch associated with each link circuit, impulse responsive means associated with each numerical switch, a dialling trunk, a relay having armatures responsive to different degrees of magnetization of said relay for connecting a calling line through sald trunk with the ima line finder associated with the last-men tioned switch to hunt for the calling line in response to the operation of said impulse receivin means. I

2. In a telephone system, a plurality of lines, line finders, a plurality of lines connected to the contact banks or said finders, a line relay for each line for establishing the calling condition or the same in said contact banks, contacts for said relay responsive to a small magnetization of its magnetic core to close. an immediate dialing circuit therethrough, and other contacts for said relay responsive to a great magnetization of said core. 1

3. In a telephone system, telephone lines, numerical switches common to said lines, a

plurality of trunks leading from said lines to said switches, means for preselecting anidle one of said trunks, means for enabling a. calling subscriber to dial immediately into said preselected trunk comprising a relay individual to each of said lines, said relay having an armature responsive to one degree of magnetization for completinga dialing circuit from the associated telephone line to the-preselected trunk, and another circuit controlling armature responsive to a difierent degree of magnetization only.

4. In a telephone'system, telephone lines,

a numerical switch common to said lines, a,

plurality of trunks leading from said lines to said switch, means for preselecting an idle In a telephone system, the combination of a telephone line, a numerical switch, a plurality of trunks leading from said line to said switch, means for preselecting an idle trunk, a marginal line relay associated with said line, said relay having an armature thereon immediately responsive to the initiation of a call on said line for closing a dialing circuit J from said line to said preselected trunk.

6. In a telephone system the combination of a telephone 11110, a plurality of trunks'com mon to said line, line finder switches for connecting said trunks to said line, means comprisingsaid line, one of said trunks and one,

of said switches for completing a dialing circuit, a mar inal line relay for said line, and

means comprising contactsor said line relay for completing a dialing circuit therethrough in shunt to a portion or the first mentioned dialing circuit.

In testimony whereof I alfix my signature.

FRITZ ALDENDORFF. 

